Rubber mixtures showing improved surface tack

ABSTRACT

Rubber mixtures containing a 2-oxohexahydropyrimidine of the general formula:   WHEREIN THE RADICALS R1 to R6 are the same or different and each individually denotes hydrogen or alkyl of from 1 to 20 carbon atoms. Such rubber mixtures possess excellent and persistent surface tack.

United States Patent Petersen et al.

[ June 24, 1975 RUBBER MIXTURES SHOWING IMPROVED SURFACE TACK lnventors:Harro Petersen, Frankenthal; Paulus Erhard, Weinheim; Hubertus Queins,Friedelsheim; Hubert Schoeppl, Mannheim, all of Germany BASFAktiengesellschaft, Ludwigshafen, Rhine, Germany Filed: July 5, 1974Appl. No: 485,805

Assignee:

Foreign Application Priority Data July 10, 1973 Germany 2334915 US. Cl.260/80.78; 260/30.2; 260/83.3; 260/85.1; 260/85.3; 260/94.7 N; 260/94.7A; 260/726; 260/739 lint. Cl C080 l/40; C08d l/OO Field of Search260/94.7 N, 94.7 A, 85.1, 260/30.2, 80.78, 83.3, 726, 739, 85.3

References Cited UNITED STATES PATENTS 8/1957 Hallenbeck 260/85.3

Primary ExaminerWilliam F. l-lamrock Attorney, Agent, or FirmJ0hnston,Keil, Thompson & Shurtleff [5 7 ABSTRACT Rubber mixtures containing a 2-oxohexahydropyrimidine of the general formula:

sess excellent and persistent surface tack.

ll Claim, No Drawings 1 2 RUBBER MIXTURES SHOWING'IMPROVED in which theradicals R to R may be the same or dif- SURFACE TACK ferent and eachindividually denotes hydrogen or alkyl i of from 1 to 20 and preferablyof from I to b and more This application discloses and claims subjectmatter Preferably of from l to 3 Carbon atoms which y P- d ib d i GermanP A ii i No, p 23 34 5 tionally be substituted by further functionalgroups 915.7, filed July 10, 1973, which is incorporated herein Such 88OH and by refere These oxohexahydropyrimidlnes may be manufac- Thisinvention relates to rubber mixtures containing lured yCy3locohdensatloh of urea of its mOIlOSUbStia tackifier based on anoxohexahydmpyrimidin tuted or symmetrically disubstituted derivativeswith 2 Non-vulcanized rubber articles such as sheets or moles of analdehyde of which at least one mole must strips must possess surfacetack if they are to be made have a character "w clip-unsaturated up intocompound or shaped articles. Such surface tack dehydes m the Presence ofaclds and m the Presence of is the only means by which the rubber can beshaped absence of an alcohol R30H, in which R3 has h m prior tovulcanization. It also avoids the occurrence of g given ab0y- SuchPTOcesses are described, for trapped air and thus provides good adhesionof the sepample, in German Pat. Nos. T330305 and 1,231,247. arate layersof rubber during subsequent vulcanization. Suitable rubbers are allCOflVentiOnal u al and syn- The rubber should remain tacky throughoutthe entire lhelic rubbers for example hOmOPOlymers of buladlstorageperiod normally required until it is processed. ene 0r isoprene or theircopolymers with styrene or ac- Tackiness is usually improved by theaddition of rylon t ile, yl u ber and hyl/propyl ne ubbers. tackifiersto the rubber. Tackifiers include rosin, couhe oxohexahydropyrimidinesShould e present in the marone resin, resins based on hydrocarbons,phen0l/- rubber mixture in amounts of from 1 to 2b andpreferaformaldehyde resins and polyadducts of phenols and bly from 2 to10 parts, for every 1100 parts of rubber. acetylene. The surface tackachieved using these addi- The mixtures may also contain conventionaladditives tives is frequently insufficient however, and above all, forubbe -g-, fillers Such as p black, SlliClC acid it diminishes rapidlywhen the rubber is stored for a and talcum, softeners such as naphtheneoils or paraffin number of days. oils, aging retardants, accelerators,activators, crosslt has now been found that 2- linkers, flameproofersand odor improvers. Incorporaoxohexahydropyrimidines have an excellentand persistion of the tackifier is carried out in conventional rubtenttackifying effect on rubber mixtures. These comber processing equipmentsuch as kneaders or roller pounds have the general formula mills attemperatures above approx. 120C.

' The following Examples the parts are by weight.

0 EXAMPLE ll 5 In separate tests, 5 parts of differentoxohexahydropyrimidines are kneaded, at 120C, into a natural 6 l Irubber mixture having the following composition: R HQ CH O 100 parts ofmasticated natural rubber,

50 parts of lamp black, 4 5 parts of a naphthene oil as softener. R RThe following compounds are used:

0 O H H C C II HN/ \NH III N CH CH 5 on y OCH 5 2 CH CH 9 V O I H IV CCH C CH I I 3 CH-N N-CH OHC-C-=CHN N-CH-C-CHO OH CH5 5 CI-Lv CH CH CH 35 O O W I! C. C VI VII HN NH HN NH OCH CH OCH K/ 0C $1 CH5 CH3 CH5 CH5VIII C l-I3 N N C H3 CH CH Compared with the untreated mixture and'witha mixture containing 5 parts of a commercial tackifier based on ahydrocarbon resin, there is seen to be a very considerable improvementin the surface tack. One measure "of the surface tack is given by theforce require d to pull apart two strips of the rubber mixturebeingtested. The strips are first pressed together under a specificpressure. To avoid tearing of very tacky strips during the test, theyare first laminated to a flexible fabric. The surface tack is givenbelow in kg and is based on an effective width of the strip of 6 mm. Themeasuring range is from to 2 kg maximum (Bussemater, van BekjR'ubberChemistry and Technology 37 (1964),

'No. 1?, 5 A New Type of Tackmeter).

Storage time of stri s l day 2 days days none V 2 0.6 0.5 0.4hydrocarbon resin 2 1.2 0.8 1 0.5 compounds II to Vlll 2 2 2 2 EXAMPLE 25 Part s of the compound of formula II are added to an oil-extendedbutadiene/styrene mixture at 120C.

The composition of the r i u fl 's-a foll s I A 50 parts ofbutadiehels'tyrene rubber 50 parts of oil-extendedbutadiene/styrenerubber oxohexahydropyrimidine of the general formula I I I. R N/ \N R2 TR6-HC CH-O-Rj in which the radicals R to R may be the same or differentand each individually denotes hydrogen or alkyl of from 1 to 20 carbonatoms, optionally substituted by further functional groups. I

1. RUBBER MIXTURES CONTAINING FROM 1 TO 20 PARTS, BASED ON 100 PARTS OFRUBBER, OF A 2-OXOHEXAHYDROPYRIMIDINE OF THE GENERAL FORMULA